M923a2 exhaust manifold bolt question

[Ford Mechanic]

I've got the exhaust manifold pulled off my 923 to repair a exhaust leak and I need to replace the bolts. Does any one know what grade bolts they were?

Mine are rusted on the cap so I can't read them. They are metric, m10x1.50x70mm I can only find them in grade 8.8 (grade 5 equivalent ) unless I want to pay 3 bucks each for the grade 10.9 (grade 8 equivalent).

If your wondering only 4 broke off. ...
Thanks
Mike

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[Tinstar]

What did the Cummins dealer say?

 

[cbrTodd]

The ones on my engine are marked 8.8. With that being said, the Cummins part number listed for them is obsolete and they were replaced by a stainless bolt of the same size.

 

[Tinstar]

Is that what you are using?

If so please post the new part number for others.

Did the busted ones come out ok?

 

[Ford Mechanic]

What did the Cummins dealer say?

No spec listed for that part other than size.

 

[cbrTodd]

Is that what you are using?

If so please post the new part number for others.

Did the busted ones come out ok?

I have never replaced mine. I was just trying to help out Ford Mechanic. The part number for the stainless bolts is 3929537.

 

[Ford Mechanic]

Is that what you are using?

If so please post the new part number for others.

Did the busted ones come out ok?

So I finally found some grade 10.9 (8 equivalent in standard) the right length at Lowes of all places. $2.10 in packs of 2
I haven't got started on the broke off ones yet, but I don't see it being a problem. I have plenty of good sharp drill bits and a set of extractors. I knew with the amount of rusted material on the shoulder of the bolt I was going to have a couple to break. It would have helped if I had a torch available at home. I'll post pics tonight or tomorrow depending on the rain.

 

[74M35A2]

Regarding stainless, it always seems like a great fix to corroded fasteners, but I think it is only medium hardness, like a grade 5 equivalent? Also, aren't engine fasteners beyond grade 8, such as grade 10? If me, I would obtain the lengths and head side thread, and then go to a Fastenal store and convert it over to studs and nuts with flat and lock washers. There is plenty of room to slide the manifold off I think?

 

[Ford Mechanic]

Regarding stainless, it always seems like a great fix to corroded fasteners, but I think it is only medium hardness, like a grade 5 equivalent? Also, aren't engine fasteners beyond grade 8, such as grade 10? If me, I would obtain the lengths and head side thread, and then go to a Fastenal store and convert it over to studs and nuts with flat and lock washers. There is plenty of room to slide the manifold off I think?

I agree, I always run into problems any time I have to use typical stainless hardware. Normally they're soft and gall quickly. Ford oe exhaust fasteners run a little different alloy. Manifold studs normally have enough nickel in the make up to prevent some rust. While the manifold to pipe connections run a black stud, (oxide coating?).

While studs are a vastly superior, and I think there is enough room to stud the manifold. It might be a little overkill for a exhaust manifold. I don't think there is much pressure inside it.

My bolts failed due to a feature on the manifold that let's water, salt, sand, dirt, etc... collect on top of the shank of the bolts. I'll post pics soon



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[Ford Mechanic]

The troughs around the bolts were holding dirt, sand, salt, water, etc..... leading to the erosion of my bolts.

Just got the manifold back from the machine shop.

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[Tinstar]

Has anyone ever had their exhaust manifold ceramic coated?

I have to do all this soon and was
wondering if it's worth it.

 

[Ford Mechanic]

So these bolts are fairly soft, so I'm thinking the were grade 5 stuff. But man are they rusted in there.

I'm going back with grade 10.9 so next time I can just hit it with the 3/8 impact!

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[74M35A2]

The free Cummins online part manual (Quickserve) indicates they are M10 x 1.5 x 70, quantity = 12.

 

[silverstate55]

I get to do this as well, glad to hear that others have had this same problem & found solutions. I plan on getting my exhaust manifold ceramic-coated (had my M35 D-turbo done, looks GREAT), should be able to start in the next month or two.

Thanks to everyone for the helpful info!!

 

[Ford Mechanic]

I'm on my last broken bolt. I've only been working on it 2-3 hrs a night, got lots of other stuff to do you know!

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[M543A2]

If you have an arc welder, go to You Tube and enter "How to use arc welder to extract broken bolts, studs, and taps". This will take you to that video and others on the subject. I have Duratrode 20-10 Stud Puller rod, 1/16 and 1/8 inch and find it works great. It has a very high tensile strength. The welding heat imparted into the bolt piece helps to break rusting, etc loose. I have even used 1/16" Duratrode to remove twisted off idle screws in carburetors. A bit of delicate welding with an arc on a carb idle screw, but it can be done.
It is also a very good idea to put hardened washers under the exhaust manifold bolts.
Regards Martin

 

[kungfu dave]

Since you guys have been talking about it, what does getting the ceramic coating done cost?

 

[Ford Mechanic]

Finally got the last bolt out! Got to do one last cleaning, then check all the ports for trash with my bore scope. Hoping she'll be running for the weekend!

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[Ford Mechanic]

Got the manifold mounted, torqued it to 35 ft lbs. Painting the first part of the exhaust pipe at the moment with VHT paint. I'll save the rest of the exhaust for a later date.

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[silverstate55]

FINALLY finished replacing my exhaust manifold gaskets. The stock design leaves a lot to be desired, it's some sort of fiber composite stuff. The photo below shows the difference between stock and current Cummins replacements. Found the gaskets on #1 & #2 cylinders failed.

It was a LOT of work; I had to remove the exhaust downpipe along with the turbo, the coolant overflow tank, and the entire thermostat housing; I let the alternator hang out of the way.